Input device for speed regulating system on motor vehicles

ABSTRACT

Input device for a cruise control system in motor vehicles, having an accelerator pedal, a switch for input of a desired speed and a determination device which increases the desired speed as a function of the duration of operation of the switch, wherein the determination device changes the function which determines the increase in the desired speed as a function of the operation of the accelerator pedal.

FIELD OF THE INVENTION

The present invention relates to an input device for a cruise controlsystem in motor vehicles, having an acceleration control device, aswitch for input of a desired speed, and a determination device whichincreases the desired speed as a function of the time of actuation ofthe switch.

BACKGROUND INFORMATION

Cruise control systems are known for motor vehicles for regulating thespeed of the vehicle at a desired speed selected by the driver. If thevehicle also has a distance sensor, e.g., in the form of a radar sensor,a stereo camera system or the like, the vehicle speed may also beregulated in such a way that a suitable safety distance from a vehicletraveling in front is automatically maintained. One example of such aregulating system, which is also known as an ACC system (active cruisecontrol), is described in “Adaptive Cruise Control System—Aspects andDevelopment Trends” by Winner, Witte, Uhler and Lichtenberg, RobertBosch GmbH, in SAE Technical Paper Series 961010, International Congress& Exposition, Detroit, Feb. 26-29, 1996.

The switch with which the driver is able to change the desired speed isusually formed by a lever on the steering wheel, which is movable eitherup or down to increase or reduce the desired speed. If this lever iskept in the upper end position for a long period of time, thedetermination device causes an incremental increase in the desired speedwith fixed increments and at fixed intervals. Accordingly, the desiredspeed is reduced when the driver keeps the lever in the lower position.When the driver releases the lever, the set desired speed is maintained.

With the help of the accelerator pedal or, more generally, with the helpof an acceleration control device, the driver may also intervenedirectly in the driving system of the vehicle and thus override thefunction of the cruise control system at any time. Thus, for example,the driver may depress the accelerator pedal to temporarily exceed theset desired speed so as to pass another vehicle. When the driverreleases the accelerator pedal again, the speed of the vehicle dropsback to the previously set desired speed. However, when the driver hasaccelerated the vehicle with the help of the accelerator pedal, thedriver may briefly tip the lever up or down so that the vehicle speedwhich has then been reached will be stored as the new desired speed. Inthis sense, the acceleration control device, i.e., the accelerator pedalis also to be regarded as part of the input device.

German Published Patent Application No. 198 02 704 describes an inputdevice using which the desired speed may be varied only incrementally,e.g., in 10 km/h increments. If the driver operates the switch whileaccelerating by using the accelerator pedal, the value closest to theactual speed then reached is stored as the new desired speed.

In general the driver thus has two possibilities of increasing thedesired speed. First, the driver may accelerate the vehicle with thehelp of the accelerator pedal and then set the new desired speed bytouching the switch. Second, the driver may hold the lever in the topposition to cause the determination device to increase the desired speedat a fixedly predetermined rate of increase.

The advantage of the first variant is that the driver himself is able todetermine by the pressure on the accelerator pedal at what rate thevehicle is accelerated, so that the driver is able to reach the newdesired speed relatively rapidly by a high rate of acceleration of thevehicle. However, one disadvantage is that the new desired speed may notbe set until the vehicle has reached that speed. Since the regulatingsystem operates with an unavoidable control lag, this may result intemporary overshooting of the actual desired speed.

This overshooting of the regulating system may be largely avoided withthe second variant. Another advantage of this variant is that the changein the throttle valve setting and/or the injection quantity using whichthe acceleration of the vehicle is induced is not determined directly bythe driver in this case but instead is calculated by the enginemanagement system of the vehicle and therefore may be optimally adaptedto the particular operating state of the engine, so that acceleration isaccomplished with optimum efficiency and therefore with favorable fuelconsumption. One disadvantage of the second variant, however, is thatthe driver must hold the lever in the upper position until the settingultimately desired has been reached by incrementally increasing thedesired speed. This is perceived in a negative sense in terms of comfortand may also result in negative effects on driving safety, in particularwhen negotiating turns at a high speed. Even if the lever is locatednear the steering wheel, the driver will be unable to grip the steeringwheel firmly with two hands as long as he is operating the lever, sothis has a negative effect on control over the steering.

The time required for setting the higher desired speed depends on theincrements and intervals by which the speed is increased as the desiredspeed is being implemented by the determination device. When theincrements are larger, the new desired speed may be achieved rapidly,but with a relatively low precision. Conversely, if the desired speed isincreased in shorter intervals, setting the speed is more difficultbecause of the very critical dependence of the desired speed on theduration of operation of the lever. When there is a rapid increase inthe desired speed, the actual speed also remains temporarily behind thedesired speed, so the driver may inadvertently set a desired speed thatis too high and then have to correct the desired speed subsequently byadjusting it back in the opposite direction.

SUMMARY OF THE INVENTION

An object of the present invention is to create an input device whichwill allow the driver to have an accurate control of the desired speedwhile also permitting a simple and rapid increase in desired speed.

This object is achieved according to the present invention by the factthat the determination device varies the function which determines theincrease in the desired speed as a function of the operation of theacceleration control device.

When the driver operates the switch without operating the acceleratorpedal at the same time, the desired speed is increased only graduallyaccording to a first function, so that precision tuning of the desiredspeed is possible for the driver. However, if the driver overrides theregulating function by using the accelerator pedal while at the sametime operating the switch to increase the desired speed, the desiredspeed is then increased according to a second function at a higher rateof increase, so the new desired speed is reached very rapidly and thedriver need not hold the switch for a long time.

This embodiment of the input device offers the driver maximum operatingconvenience in different driving situations. For example, if the cruisecontrol system is not combined with a distance regulating system, thereis often the need to adjust the desired speed to the speed of thevehicle traveling in front with a relatively precise control. In thiscase the driver is able to adjust the desired speed with precisionmerely with the help of the switch without using the accelerator pedal.However, if the driver would like to drive at a much higher desiredspeed for a longer period of time, e.g., after leaving a reduced speedzone, the driver will then first operate the accelerator pedal toaccelerate the vehicle quickly. At the same time, the driver may thenvery rapidly set the new desired speed by using the switch and he maythen take his foot from the accelerator pedal again while the vehicleautomatically accelerates further until reaching the desired speed.

This input device has also proven to be particularly advantageous, e.g.,in the situation in which a vehicle traveling in front is being followedby a vehicle having an ACC system, but the driver of the vehicle havingACC then decides to pass the other vehicle because the driver of thevehicle in front is driving at a very irregular speed. In this case thedriver of the vehicle having ACC will initiate the passing maneuver bydepressing the accelerator pedal and will then at the same timesimultaneously increase the desired speed to a level that ensures thatthe distance from the vehicle being passed will increase by brieflytouching the switch. When the passing maneuver is concluded and thedriver releases the accelerator pedal, the vehicle then drops back tothe new slightly increased desired speed.

The input device is preferably combined with a display device whichinforms the driver of the particular valid desired speed. The desiredspeed may be displayed with the help of LEDs, for example, which areintegrated into the tachometer of the vehicle. Alternatively, anumerical display of the desired speed is also conceivable.

The function which determines the increase in the desired speed when thedriver also operates the accelerator pedal may be designed in such a waythat the value range contains only “rounded” speed values, e.g., 50km/h, 60 km/h, 70 km/h, etc. Thus, when the vehicle has passed aconstruction area, for example, where the speed limit was 60 km/h andthen enters a zone where the speed limit is 100 km/h, the driver is ableto increase the desired speed very rapidly to 100 km/h by using theswitch, i.e., in only four increments, while at the same time initiatingthe acceleration phase by depressing the accelerator pedal. Once the newdesired speed has been reached, the driver may adjust the desired speedin fine increments merely by operating the switch, e.g., in incrementsof 1 or 2 km/h, without operating the accelerator pedal at the sametime.

The functions which determine the increase in the desired speed by thedetermination device may differ in both the size of the increments aswell as the length of the intervals during which these increases takeplace. These functions may also be nonlinear functions which, forexample, cause the desired speed to first increase at a low rate ofincrease when the switch is operated and then to increase with a higherrate of increase when the switch is operated for a longer period oftime.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a block diagram of a cruise control and the respectiveoperating and display elements.

FIG. 2 shows a display device which is integrated into a speedometer onthe dashboard of the vehicle.

FIG. 3 shows a flow chart to illustrate the functioning of adetermination device for the desired speed.

FIGS. 4 and 5 show examples of functions for changing the desired speed.

DETAILED DESCRIPTION

Since the design and operation of a cruise control having an ACCfunction are known, FIG. 1 shows only the most important components in ablock diagram. A sensor device includes a distance sensor 10, e.g., aradar sensor, which measures the distance and relative speed of avehicle traveling in front. If multiple target objects are detected bythe radar sensor, e.g., multiple vehicles or stationary targets such asroad signs and the like, the target object formed by the vehicletraveling directly in front of one's own is selected by plausibilityanalysis.

The signals of the distance sensor are analyzed in an electronic cruisecontrol device 12 formed by a microcomputer, for example. Cruise controldevice 12 acts on the drive and brake systems of the vehicle to regulatethe driving speed either at a desired speed selected by the driver or ata suitable distance from the vehicle traveling in front.

This cruise control function, referred to here as an ACC function, isactivated by the driver by operating an ACC button 14. If a desiredspeed had already been stored previously, operation of the ACC buttonwould have the function of causing the regulation at this desired speedto be resumed (“resume”). Otherwise the desired speed is set by thedriver briefly operating a switch 16 (touch button switch) after thevehicle has reached the desired speed. Additional or persistentoperation of switch 16 causes an incremental increase in the desiredspeed. Similarly, operation of a switch 18 causes an incrementalreduction in the desired speed. Switches 16, 18 are formed in practiceby a lever which is located on the steering wheel and is movable up toincrease the desired speed or down to reduce the desired speed. Theportion of cruise control 12 that determines the desired speed as afunction of the commands input via switches 16, 18 is referred to asdetermination device 20.

By operating the accelerator pedal, the driver may override the ACCfunction to accelerate to a higher speed temporarily. Operation of theaccelerator pedal is detected by an accelerator pedal sensor 22.

The cruise control may be deactivated by a touch button switch 24. Adisplay lamp 26 indicates whether the ACC function is active orinactive.

FIG. 2 shows a speedometer 28 such as that usually provided on thedashboard of a motor vehicle. Speedometer 28 has the usual speed scaleand a tachometer needle 30 and also includes display lamp 26 for the ACCfunction as mentioned above.

The display device also includes a plurality of LEDs 32 which aredistributed uniformly with a resolution of 2 km/h over the speed scalein the speed range above 40 km/h. One of these LEDs 32 lighting upindicates the desired speed which has been set with the help of one ofswitches 16, 18. In the example shown here, the desired speed has beenset at 58 km/h and LED 32 a assigned to this speed lights upaccordingly.

The function of determination device 20, inasmuch as it relates toincreasing the desired speed, will now be explained on the basis of theflow chart shown in FIG. 3. The flow chart shows a program routine whichis called up at certain intervals, e.g., every 10 ms. After the start ofthe program, there is a query in step S1 to determine whether switch 16has been operated. This step is repeated until operation of the switchhas been ascertained. In step S2, current speed V_(actual) is then setas new desired speed V_(setpoint).

After a brief waiting period (step S3), there is a query in step S4 bychecking accelerator pedal sensor 22 to determine whether theaccelerator pedal has been operated. If this is the case, it is assumedthat the driver wishes to increase the desired speed as rapidly aspossible. Therefore in step S5, an increment A for the increase in thedesired speed is set at 10 km/h. Otherwise increment A is set at asmaller value, e.g., at 2 km/h, in step S6. There is again a query instep S7 to determine whether switch 16 is still being operated, i.e.,whether or not the driver has been holding switch 16. In this case, thedesired speed is increased again by 10 km/h or by 2 km/h in step S8, andafter a certain interval has elapsed (step S9), the routine jumps backto step S7. As long as the driver continues to hold down switch 16,steps S7 through S9 are run through cyclically and the desired speed isincreased gradually in increments Δ. While the desired speed is beingincreased incrementally, cruise control 12 remains active so that theactual speed follows the desired speed with the regulating time lagdetermined by the system.

When the driver releases switch 16, the program is terminated and thedesired speed reached then is saved.

The driver may thus set the current speed as the new desired speed bytouching switch 16 only briefly—regardless of whether the acceleratorpedal is being operated. In addition, the driver may make a precisionadjustment of the desired speed with a resolution of 2 km/h bycontinuing to operate switch 16 without operating the accelerator pedal.When the driver first depresses the accelerator pedal and then operatesswitch 16 and holds it, it is assumed that the driver would like toaccelerate and substantially increase the desired speed. This isfacilitated by having the increase occur with a larger increment Δ=10km/h and consequently at a greater rate of increase with the same timelag in step S9. In the example shown here, the position of theaccelerator pedal is not queried repeatedly, so the high rate ofincrease is maintained as long as the driver continues to operate switch16 even if the driver has lifted his foot from the accelerator pedal inthe meantime.

The increase in the desired speed is displayed by LEDs 32 of the displaydevice. The driver may thus track the increase in desired speed and mayselect the desired speed by releasing switch 16 at a suitable moment.Thus the driver's attention is demanded only for a brief period of timebecause of the high rate of increase.

In the example shown here, the increase in the desired speed is alsoaccomplished with a large increment of 10 km/h, always starting from theinstantaneous desired speed. If the desired speed is first 58 km/h, itis then increased incrementally to 68 km/h, 78 km/h, etc. However, theprogram may optionally modify this, so that in the first execution ofstep S8 following step S5, the desired speed is increased only to thenext higher rounded-off value, i.e., for example, 58 km/h is firstincreased to 60 km/h and then to 70 km/h, 80 km/h, etc.

Instead of increasing the size of increment A, as done in step S5, therate of increase in the desired speed may also be increased by reducingthe time lag in effect in step S9 with no change in the increment.

Although in the two examples described above, the desired speed isincreased incrementally but linearly on the whole, the desired speed mayalso be increased according to a nonlinear function over time. Examplesare shown in FIGS. 4 and 5. Curves 34 and 36 in FIGS. 4 and 5 representfunctions ΔV(t) which indicate the increase in desired speed as afunction of time t, during which switch 16 is held in the operatedposition. In FIG. 4 the desired speed increases first slowly and thenprogressively more rapidly. With a much longer holding time, the curveflattens out again and then corresponds to a linear increase in thedesired speed at a constant rate of increase. The change in the desiredspeed is always accomplished in the same increments in FIG. 4 but with adifferent time lag. In FIG. 5, however, the desired speed is increasedin constant intervals but by variable increments. The desired speed hereincreases only slowly at first, but then increases more rapidly andfinally at a constant, relatively high, rate of increase.

If accelerator pedal sensor 22 is designed in such a way that it mayalso quantitatively measure the extent of operation of the acceleratorpedal, then the rate of increase in the desired speed may also be variedas a function of the intensity of operation of the accelerator pedal.

1-7. (canceled)
 8. An input device for a cruise control system in amotor vehicle, comprising: an acceleration control device; a switch forinputting a desired speed; and a determination device for increasing thedesired speed based on an operating time of the switch, wherein thedetermination device changes at least one of the functions whichdetermine an increase in the desired speed based on an operation of theacceleration control device.
 9. The input device as recited in claim 8,further comprising: a display device for displaying the desired speedthat is currently valid.
 10. The input device as recited in claim 8,wherein the acceleration control device is an accelerator pedal.
 11. Theinput device as recited in claim 10, wherein the determination deviceincreases the desired speed at a higher rate of increase when theaccelerator pedal is also operated while the switch is operated.
 12. Theinput device as recited in claim 8, wherein the determination deviceincreases the desired speed by an increment after each time interval ofincrease has elapsed as long as the switch is operated.
 13. The inputdevice as recited in claim 12, wherein the functions which determine theincrease in the desired speed differ an the amount of the increment. 14.The input device as recited in claim 12, wherein the functions whichdetermine the increase in the desired speed differ in a length of a timeinterval of increase.